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Joseph Lobel ’13 Tracks Mysterious Jumping Genes

In the DNA of every cell in your body, segments of DNA are constantly jumping and shifting locations. These jumping segments are called transposons and they usually contain the building blocks for genes, but do not provide your body with blueprints like regular genes. But in a group of microorganisms called ciliated protists, some types of transposons (called Telomere-Bearing Element, or TBE, transposons) do contain genes, and they are sometimes even expressed. Working under Assistant Professor of Biology Wei-Jen Chang, Joseph Lobel ’13 is spending his summer trying to detect and sequence these elusive, mobile genes.

Lobel is working mostly on a ciliated protist species called Uroleptus. This species branched off from other ciliates before another species called Oxytricha trifallax had evolved separately. Oxytricha trifallax is already known to have four functional genes on its TBE transposon, which has already been sequenced. Transposons carrying multiple genes are peculiar because most transposons carry only one gene whose sole purpose is to help transposons “jump” from one spot to another in the host genome. Some bacterial transposons evolved to carry more than one gene and the extra genes often code for enzymes against antibiotics. But, the functions of the extra genes found on TBE transposons are unknown. By comparing Uroleptus’ transposon sequence to that in Oxytricha trifallax, Lobel hopes to understand how a multigene transposon arose.

But finding such a slippery sequence is difficult and often depends on happenstance. Lobel will be using multiple different methods to detect the transposon, but his current approach looks promising. He takes millions of known, sequenced transposons and injects them into a sample of Uroleptus’ DNA. If one of the inserted sequences lands near an already-known region in the genome, Lobel can run a polymerase chain reaction (PCR) to amplify the unknown segment between the two known regions and eventually sequence it. Working this way, Lobel will hopefully find the TBE transposon he is looking for in Uroleptus and with any luck, he will find some similarities to help determine when and how these genes evolved.

Spotting these genetic differences could have great significance in scientists’ larger goal in plotting the evolutionary history of every organism. “Hopefully we will see some similarities in two or three of the genes [on the transposon] to show that the fourth gene evolved after Uroleptus and before Oxytricha trifallax. We want to know how these genes effect the fitness of the organism,” Lobel said. “It’s odd that these protists have mobile genes. It is really interesting, searching for why this anomaly exists.”

A rising sophomore, Lobel enjoys rock climbing, whether he is on the wall on campus or has found a nearby crag. He also likes to cook, especially making his own bread, and volunteers with HAVOC during the school year. He plans to be a biology or biochemistry major.